In decorative laminates used as materials for interior and exterior of buildings, there are various kinds of those such as, beginning with inorganic decorative laminates, metal siding, vinyl chloride-extruded siding, foamed lightweight concrete panels, metallic plates, tiles and so on. The surface of these decorative laminates is usually subjected to various patterning for the purpose of keeping a substrate from deteriorating, or improving the designability of appearance.
Recently, higher designability is increasingly demanded with regard to the patterning of these decorative laminates for interior and exterior of buildings. There is proposed a method of forming a high-definition image with an ink-jet technique (Patent Document 1).
The decorative laminates patterned in such a printing system, in particular, those for outdoor use, are demanded to have higher water resistance and weathering resistance of ink. Thus, pigments are used as a colorant for ink instead of dyes. An ink using a pigment as a colorant, in particular, a water-based ink is usually insufficient in printing density and the dispersion stability of pigments. When an ink-jet printer is used as a means of printing, there is a problem in production that the clogging of a nozzle tends to be caused in its head.
In this kind of decorative laminates for buildings, the intended purpose of coating the surface of its substrate is to shield the substrate's surface from a deteriorating factor like water or oxygen to keep the substrate from deteriorating. Thus, a prime coat is formed on the surface of the substrate before patterning in order to accomplish this purpose. The surface condition of such a prime coat thickens out of the need, and hence ink droplets discharged on the prime coat disposed on the surface of the substrate are spread on the surface of the prime coat without absorbing them into the prime coat. Thus, it is difficult to draw a precise image. For this reason, it is necessary to preliminarily form a receiving layer prior to ink-jet coating in order to improve the ink absorbability of the prime coat. There is proposed that an inorganic filler, such as silica fine particles, having high oil absorption is compounded into a prime coating material (Patent Document 2).
For the purpose of performing high definition patterning in a printing system, the surface of a substrate is coated with a coating material for the formation of a surface to be printed which comprises hydrophilic cross-linked resin particles, to form an ink receiving layer having excellent ink absorbability. Moreover, a water-based ink which substantially comprises no binder such as a resin or the like is used as ink, which becomes difficult for the clogging of a nozzle to be caused even if the nozzle bore diameter of the head of an ink-jet printer is made smaller, but also ink running can be sufficiently prevented. Thereby, there is proposed a method of producing a building material having designability which is capable of easily printing a high definition pattern (Patent Document 3). There is also proposed a method of producing a building material having designability which is intended to improve ink durability and prevent ink running, by coating the surface of a substrate with a coating material for the formation of a surface to be printed to form an ink receiving layer in the same manner, and then preliminarily-discharging a coloring ink containing a reactive compound A on the receiving layer to form an image and thereafter discharging a clear ink containing a reactive compound B, which generates curing reaction with the reactive compound A, into this ink image or, on the contrary, preliminarily-discharging a clear ink containing a reactive compound B to form a clear region and thereafter discharging a coloring ink containing a reactive compound A (Patent Document 4).
In these decorative laminates for buildings, various coating materials or patterning inks used in their production process are intended to reduce environmental pollution or improve working environment, as is the case for other coating or printing industry. In particular, the decorative laminates for outdoor use is refraining from the use of a solvent-based coating material or ink which discharges a large amount of a volatile organic compound (VOC) for the purpose of preventing sick house syndrome from being developed, and the substitution of a water-based coating material or ink is proceeding.
In the above-mentioned conventional decorative laminates for buildings, when a water-based coating material is used as a coating material for forming a prime coat (ink receiving layer) and/or a water-based ink is used as an ink for forming the colored pattern or design (printing layer), the ink receiving layer or printing layer is inferior in water resistance because they are formed by a coating material or ink using an aqueous solvent. Even if a pigment having excellent water resistance and weathering resistance is used as a coloring material for a water-based ink, for example, when it is weathered outdoors, the ink receiving layer or printing layer is easily deteriorated and the desired pattern formed on the printing layer is broken down. Thus, for the purpose of protecting the ink receiving layer or printing layer formed on the surface of the decorative laminates for buildings, there is carried out coating the printing layer with a clear coating material to form a top coat layer made from the clear coating material having excellent coat durability such as water resistance, weathering resistance and so on.
However, in the case of forming a top coat layer with a water-based clear coating material, the ink forming design in the printing layer is redissolved in an aqueous solvent of the water-based clear coating material applied thereon and hence ink running occurs in the printing layer. In some cases, peeling occurs between an ink receiving layer and a top clear layer, so that sufficient protection performance cannot be necessarily obtained in the water resistance and ink running of the printing layer. Thus, there is a need to use a solvent-based clear coating material as a clear coating material for forming a top coat layer from the viewpoint of the quality stability of products.
There is further proposed a technique of using an active energy ray-curing type ink-jet ink as an ink-jet ink for providing a high definition pattern (Patent Document 5). The active energy ray-curing type ink is excellent in quick-drying properties because it is cured immediately through active energy ray irradiation, it does not need a receiving layer because the ink membrane contains a resin component, and the curing proceeds only through active energy ray irradiation unlike in the case of a resin-containing ink-jet ink. In these reasons, the clogging of a head portion due to the solidification of a resin does not occur and hence discharge stability is excellent. Further, an amount of emission of VOC is very small because almost total amount of the applied ink is fixed as a coat on a substrate, and hence there is an advantage of being able to reduce environmental loads.
However, the coat formed by the active energy ray-curing type ink is low in the adhesion to a substrate and/or in the adhesion between an ink layer and a top coating layer when further forming the top coating layer on the coat of the active energy ray-curing type ink. Thus, delamination tends to take place and thereby there is a problem of reducing weathering resistance.